DIGESTIVE SYSTEM 2 Flashcards
what are the digestive accessory organs?
salivary glands
liver
gallbladder
pancreas
what do the salivary glands do?
secrete lubricating fluid & enzymes that break down carbs
what does the the liver do?
Bile production; storage
what does the gallbladder do?
Stores & concentrates bile
what does the pancreas do?
Exocrine cells (fluid & enzymes), endocrine cells (hormones)
where are the small salivary glands?
Situated in submucosa of oral cavity + tongue
how are the small salivary glands grouped?
Lingual Labial Buccal Molar Palatine
what are the 3 types of large salivary glands?
sublingual
submandibular
parotid
where is the sublingual gland?
Beneath tongue
Many ducts
where is the submandibular gland?
Floor of mouth
Along inner surface of mandible
Ducts behind teeth
where is the parotid gland?
Largest, empties into mouth at the second molar
what kind of glands are all the salivary glands?
All tubulo-acinar glands
what are the large salivary glands?
Glands close to oral cavity secrete mucus
what so the Sublingual glands secrete?
Mainly mucus acini
what do the Submandibular glands secrete?
Serous and mucus acini
what do the Parotid glands secrete?
Almost exclusively serous acini
what is the liver?
Largest gland of body (and largest internal organ)
Highly vascularised
what are the 4 lobes of the liver?
2 major – left + right (largest)
2 minor – caudate + quadrate
what is the liver surrounded by?
CT
what does the liver function as?
an exocrine gland (secretes onto an epithelium via a duct)
where does the liver receive blood from?
2 vessels
Hepatic artery (oxygenated, from aorta)
Hepatic portal vein (from digestive system + spleen)
what is the percentage of arterial blood in the liver?
25%
what is the percentage of venous blood in the liver?
75%
where is blood discharged from the liver?
into small vascular channels called sinusoids (sinusoidal capillaries)
what are kupffer cells?
Sinusoidal macrophages
Destroy bacteria
Degrade worn-out blood-cells
where does the blood flow out of the liver in order?
capillaries, central vein, hepatic vein, inferior vena cava
what are hepatic sinusoids lined by?
discontinuous sinusoidal epithelium
what is the liver lobule?
Basic functional unit of the liver
what are the specialised epithelial cells in the liver?
hepatocytes
what is a lobule composed of?
Terminal hepatic venule
Interconnecting plates of hepatocytes
Peripherally arranged portal triads
what is the lobule delimited by?
by CT, called interlobular septum
what are the 3 hepatocyte zones of the liver lobule?
periportal
mid zone
centriolobular
what is the periportal hepatocyte zone?
Highest nutrient component
Most oxygenated
Highest toxin conc.
what is the mid zone hepatocyte zone?
no sharp boundaries
what is the centriolobular hepatocyte zone?
Lowest nutrient component, but larger glycogen + fat deposits
Least oxygenated
what is the organic composition of bile?
bilirubin
what is the inorganic composition of bile?
bile salts
what is bile produced by?
hepatocytes
where does bile pass into?
bile canaliculi
where do canaliculi carry bile?
to bile duct (counter-current to blood flow)
what is the bile duct lined by?
cholangiocytes
what are the features of cholangiocytes?
Short microvilli
One cilium per cell
Senses change in flow (mechanosensory)
what are the Terminal bile ducts lined with?
cuboidal epithelium
what are the Intrahepatic bile ducts?
Coalesce into left + right hepatic ducts
Unite to form common hepatic duct
what are the Intrahepatic bile ducts lined by?
Columnar epithelium
where does the cystic duct travel to and from?
to/from gallbladder
where does the common bile duct travel to?
to the duodenum
what is the gallbladder?
Ovoid sac with muscular wall Can distend (swell)
what is the function of the gallbladder?
Concentrates and stores bile
where are H2O + ions absorbed?
by mucosa
where does the gallbladder receives watery bile from?
the hepatic duct
where does the gall bladder empty thick, concentrated bile into?
the common bile duct
what are the 3 layers of the gallbladder?
mucosa
muscularis externa
adventitia
what is the mucosa layer of the gallbladder made of?
Columnar epithelium with microvilli
what does the mucosa layer of the gallbladder not contain?
No mucus producing cells
No muscularis mucosae or submucosa
what is the mucosa layer of the gallbladder arranged in?
in plicae
how is concentrated bile expelled in the mucosa layer of the gallbladder?
by contraction of smooth muscle wall
what is Cholecystokinin in the gallbladder?
CCK is a peptide hormone released from inclusion cells in duodenum
what does CCK do?
Reduces digestive motility + gastric emptying
where is the pancreas located?
behind the stomach
what is the pancreas?
Elongate organ
Retroperitoneal
what is the structure of the pancreas?
No distinct capsule
Covered by a thin layer of connective tissue
what does the pancreas function as?
Endocrine and exocrine functions
what is the exocrine part of the pancreas composed of?
tubulo-acinar glands
what does the exocrine part of the pancreas secrete?
pancreatic juice Alkaline fluid composed of enzyme precursors
what is the exocrine function of the pancreas made of?
Single layer of epithelial cells form secretory acini
what are the ducts of the pancreas?
acini, interlobular, pancreatic, bile duct
what is the acini duct?
1st part of intercalated duct
what is the interlobular duct made of?
columnar epithelium
what is the pancreatic duct made of?
columnar epithelium
what does the bile duct secrete into?
the duodenum
what does the endocrine part of the pancreas contain?
islets of langerhans
where do the islets of langerhans secrete products to?
into pancreatic ducts
what do the islets of langerhans contain?
Contain a variety of neuroendocrine cells
what are Beta cells?
Secrete: insulin + amylin
Stimulates glycogen, protein and fatty acid synthesis
what are Alpha cells?
Secrete: glucagon
Generally opposite actions of insulin
what are Delta cells?
Secrete: somatostatin
Locally acting hormone
Inhibits other endocrine cells
what are PP-cells (pancreatic polypeptides)?
Stimulates gastric chief cells
Inhibits bile secretion
what are Epsilon cells?
Secrete: Ghrelin
Stimulates appetite
what are EC (enterochromaffin) cells?
Secretes:
Secretin: controls secretion of other hormones
Motilin: stimulates gastric activity
Substance-P: wide range of functions
what are D1 cells?
Secrete: VIP (Vasoactive Intestinal Peptide)
Relaxes stomach and gallbladder
Reduces arterial BP
